Prove2Me

Lean-Workbook Plus 65703: Trigonometric identity

Proved
WorkbookRestored.plus_65703

by wamlart · Sep 12, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

lean-workbookrestored-importssource-checked

For real α,β,γ\alpha,\beta,\gamma, if α=π−(β+γ)\alpha=\pi-(\beta+\gamma), then sin⁡α=sin⁡(β+γ)\sin\alpha=\sin(\beta+\gamma).

Source: Lean-Workbook row lean_workbook_plus_65703 (Apache-2.0). The unchanged proposition comes from the original record; its missing mathematical imports and namespaces are restored here.

Preamble
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic
open Real
Formal statement
theorem WorkbookRestored.plus_65703 (α β γ : ℝ) (h : α = π - (β + γ)) : sin α = sin (β + γ)   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_65703; immutable original Prove2Me node 95f9cfb9-31d6-478c-8c63-cee93673027f

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